A golf club head, and in particular the crown of the golf club head, may be divided into several regions for purposes of illustrating the effects of forces generated by the impact of a golf ball against the face of the golf club head. The first region is in communication with the impact surface defined by the face of the golf club head such that the impact of a golf ball at the face directly causes internal stresses to be generated by the impact force of the golf ball that travels through and directly affects the first region of the crown. In addition, a second region of the golf club head may be defined along the crown between the first region and the back of the golf club head such that relatively lower stress and vibration should be felt in the second region by the forces generated after the impact of a golf ball against the face in comparison to the first region of the golf club head.
Many golf club heads are formed with a number of relatively large apertures defined along the second region of the crown in order to lessen the weight of the golf club head and/or change its center of gravity. However, this arrangement of large apertures can cause a disproportionate or uneven distribution of internal stresses through the second region of the crown when a golf ball strikes the face of the golf club head. In particular, stress risers, which are pockets of concentrated stress, can develop in the material of the crown between the apertures. Stress risers are caused when internal stresses generated by the impact force of a golf ball are distributed unevenly through the second region of the crown and focused on particular portions of the golf club head. This disproportional distribution of internal stresses through the second region of the crown can cause the structural failure of the golf club head over time as the area between the apertures crack or otherwise fail because of the excessive internal stresses being generated in the second region of the crown due to the bending forces being focused on a particular area of the crown after repeated impacts with a golf ball.